1. Technical Field
The present invention relates to a position control method, and more particularly, to a control method for implementing high position precision.
2. Related Art
Robots having a joint link (hereinafter, referred to as an arm) of multiple joints are used in apparatuses having many assembled devices or the like. When such robots move the arm and stop the arm, the arm vibrates. While the arm vibrates, a robot hand that is disposed on the tip end of the arm also vibrates. While the robot hand vibrates, it is difficult for the robot hand to perform an operation such as an operation of gripping the work. Accordingly, the operation needs to wait for the vibration of the robot hand to stop.
In order to improve the productivity of the robots, a method of shortening a vibration time of the robot hand is disclosed in Japanese Patent No. 3,883,544. According to the method, an angle sensor that detects the rotation angle of the arm is disposed in an actuator of the arm. In addition, an angular velocity sensor that detects the vibration of the arm is disposed on the hand side of the arm. Then, the low-frequency component of the output of the angle sensor is extracted by using a low-pass filter, and the high-frequency component of the output of the angular velocity sensor is extracted by using a high-pass filter. Next, the operation of the arm is detected by composing the output of the angle sensor and the output of the angular velocity sensor. Then, the vibration of the arm is suppressed by controlling the arm in response to the operation of the arm.
The actuator is formed by a motor and the like and is driven by being supplied with power. Then, when the driving time is long, the motor generates heat. As the heat of the motor is conducted to the arm, the temperature of the arm rises. As the temperature of the arm rises, the arm expands. Accordingly, the length of the arm may be changed. In addition, when the robot hand grips the work, the arm may be bent due to the weight of the work. In such a case, the position of the robot hand with respect to the actuator changes. A method of controlling the arm with high position precision even in a case where the arm is deformed as described above is desired.